This invention relates to plumbing, to plumbing traps and plumbing couplers made of flexible pipe, and to plumbing traps having a shape suitable for use in conjunction with drainage of condensate from refrigeration units and in particular with air conditioning units or the like.
An air conditioner employs a heat exchanger for exchanging heat with room air which exchanger is generally much colder than the room air when cooling a space during a hot day. As a motor-driven fan draws air through a filter and over the metal fins of the heat exchanger (and then into the space being conditioned) moisture in the air tends to condense and fall down into a drip tray, from where the condensate is led through a pipe into a drain on a continuously connected basis. As is usual in plumbing practice, a trap comprising a xe2x80x9cUxe2x80x9d shaped bent pipe and containing enough water to fill the base of the xe2x80x9cUxe2x80x9d is commonly employed to prevent bad smells from the drain from being drawn into the air conditioner by negative pressure developed by the fan, and so into the space being conditioned, where a smell would have a high nuisance value at least.
It is usual to provide some clear tubing at the connection to the tray, in order to demonstrate to a service engineer the presence of water at this point and hence a likely blockage. The remainder of the trap is typically made of rigid plastics or metal pipe. Current types of xe2x80x9cUxe2x80x9d trap are unduly complex, difficult to maintain because the amount of water within the trap cannot easily be ascertained, and are not adaptable to being fitted into warped positions. There is a requirement that a small negative pressure be sustainable (especially if the inlet filter becomes occluded), so that typical traps resemble siphons although with the first leg entered by condensate being higher than the second leg so that internal water can rise a little more within the first leg.
Within the recent patent literature, few references to air conditioning system condensate traps were found. Chaves (U.S. Pat. No. 5,644,925, July 1997) describes a trap having an internal valve capable of preventing undesired air movement in either direction while allowing water to pass. Jacob (U.S. Pat. No. 3,905,203, September 1975) describes a complex condensate collector including a fine capillary structure, which might be prone to algal contamination.
In relation to traps in general, Lamond (U.S. Pat. No. 4,516,278, May 1985) describes an xe2x80x9cPxe2x80x9d trap of conventional configuration for use underneath a sink, where the trap is made from a flexible pipe. The stated advantages include that fitting is easier, congealed material may be shifted by external manipulation, and if the pipe is also transparent, the contents of the trapxe2x80x94water and perhaps solid and even wanted objects can be seen. Bresnahan (U.S. Pat. No. 5,063,616, November 1991) describes a similar trap of conventional configuration; a flexible xe2x80x9cSxe2x80x9d bend trap.
The term xe2x80x9cflexiblexe2x80x9d as used in this specification means that the examples of the trap as will subsequently be described can be bent about by hand pressure at room temperature and otherwise manipulated yet are sturdy enough to not collapse when the interior is subjected to a mild negative pressure of the amount expected in use.
By xe2x80x9cthermoplasticxe2x80x9d we refer to a plastics material capable of becoming softened at a softening temperature and if distorted by external forces while softened, of holding that distortion in a fixed state when cooled.
It is an object of this invention to provide an improved trap for connection to a drainage system, or at least to provide the public with a useful choice.
In a first broad aspect the invention provides a flexible trap or coupling for connection between a conduit (a pipe) capable of delivering a liquid and a conduit (a pipe) capable of disposing of the liquid such as toward a drain, wherein the trap comprises a hollow, elongate (that is, tubular) flexible (as herein defined) member in the form of an open loop having a substantially constant rate of bending and having a configuration resembling the Greek xe2x80x9calphaxe2x80x9d (xcex1) symbol; the flexible trap having an inlet at a first free end continuous with a first limb, the first limb being continuous with an intermediate part and then a second limb, in turn continuous with an outlet at a second free end; the flexible trap being capable, when used in an orientation wherein the inlet and the outlet are at a similar height and the intermediate part is below the inlet and below the outlet, of retaining a sufficient amount of the liquid within at least the intermediate part to allow operation as a plumbing trap by holding and allowing the passage of the liquid yet being capable of blocking the passage of a gas.
Preferably the flexible material is selected from a range of flexible plastics materials including polyvinyl chloride and the like.
Preferably the flexible plastics material is a thermoplastic, as herein defined.
Preferably the flexible material is effectively transparent so that an amount of liquid held within may be inspected from the exterior.
Preferably the plastics material is substantially transparent so that dirt, algae, blockages, and the like are visible through the walls.
Preferably the flexible material, though effectively transparent, is coloured with an effective amount of a dye capable of absorbing light used by plant life, so that the growth of said plant life is discouraged.
Preferably the flexible material is capable of being installed in a permanently distorted configuration so that connections may be made between misaligned pipes, yet the flexible material will not exhibit long-term cracking.
Optionally, a mechanical one-way valve is included within the flexible trap so that the trap function is retained even if insufficient liquid is present within the trap.
Preferably the flexible material is capable of being used in a permanently distorted configuration so that connections may be made between misaligned pipes.
Preferably the flexible material is sufficiently flexible to permit removal in order to clear internal blockages, but is not so weak that the walls will collapse together during use.
Preferably the flexible material is capable of withstanding vibration applied between one end and the other.
In a second broad aspect the flexible trap as previously described in this section may be considered as a flexible coupling, the slightly altered purpose being for bridging a gap between a first conduit and a second conduit particularly in situations where one conduit is capable of exhibiting motion in relation to the other, wherein both (a) the flexible material comprising the flexible coupling, and (b) the xe2x80x9calphaxe2x80x9d (xcex1) configuration which has the effect of distributing the strain over the entire loop serve to maintain the integrity of the coupling despite relative movement.
In a third broad aspect this invention provides a method for the manufacture of preformed traps of a flexible hollow elongated material as previously described in this section, including the steps of: taking a suitable length of pipe, fitting a coil of wire within the pipe, softening the pipe using heat (such as within an oven), placing the pipe in a jig in an over-bent shape to allow for some springing back, optionally returning it to the oven, cooling the pipe while holding it in the jig, and removing the coil of wire by twisting one end so that the coil diameter is reduced and the coil can be withdrawn.
In a related aspect, another method for manufacture includes the steps of: taking a length of pipe, placing a restriction at one end of the pipe, passing a flow of heated air through the pipe from the other end under a slight positive pressure capable of causing distension, and when the pipe is soft and able to be distorted, wrapping it around a former of a suitable diameter and then continuing to pass now cooled gas through the pipe also under a slight distending pressure (capable of preventing loss of patency of the lumen) until the pipe is no longer soft.
Preferably the former has sides also tending to prevent flattening of the softened pipe.
The description of the invention to be provided herein is/are given purely by way of example and are not to be taken in any way as limiting the scope or extent of the invention.